Research into reproduction will be carried out to understand and ultimately control the reproductive process. The proposed research will deal with the biochemistry and physiology of uterine smooth muscle. Uterine contractility will be studied in a 3-pronged attack on the subcellular level: 1) The contractile proteins, 2) sarcoplasmic reticulum calcium-binding, 3) hormonal regulation of calcium transport; clinical studies. 1) Uterine troponin will be split into several components using chromatography or electrophoresis. The components will be characterized by acrylamide gel electrophoresis, amino acid analysis, ultracentrifugation, effect of ATPase activity of desensitized actomyosin, and calcium binding. Actomyosin and myosin will be extracted from uterine muscle and characterized by ultracentrifugation, amino acid analysis and ATPase assay . 2) Calcium binding or uterine sarcoplasmic reticulum form pregnant and non-pregnant animals, and humans will be studied using atomic absorption spectroscopy. It will be attempted to extract a calcium binding protein from the membranes of the sarcoplasmic reticulum. This protein will be purified and characterized and calcium binding quantitatively assayed by equilibrium dialysis. 3) Effects of hormones and pharmacological agents on calcium binding of uterine SR will be evaluated - clinical implications. Our long-range interest is the mechanism of the onset of labor, presently unknown, the role of the prostaglandins in initiating labor and in the human reproductive process. Such knowledge must be the basis for their clinical use in the augmentation of labor, thus leading to fewer retarded babies, as well as in fertility and population control.